The principal objective of this study is to elucidate the structural and metabolic functions of polyunsaturated fatty acids and phospholipids with particular reference to their modulation by ethanol. Several approaches to this problem were taken, including studies of cellular lipid composition, membrane asymmetry, fatty acid oxygenation and dietary supplementation. In particular, these studies focused on the major polyunsaturate of brain, docosaheaenoate (C22:6w3) and, to a lesser extent, on arachidonate (C20:4w6). Progress has been made in the development of a covalent labelling technique that allows the study of aminophospholipid molecular species composition and membrane topology. Data for reference purposes has been obtained for more than 50 species in the human erythrocyte. Generally, the phenomenon of molecular species asymmetry has been confirmed, i.e. polyunsaturates are selectively localized on the cytoplasmic leaflet of the plasma membrane. Dietary supplementtation with w-3 fatty acids leads to replacement primarily of alkenyl-20:4w6 phosphatidylethanolamines (PE) with the corresponding 20:5w3 or 22:6w3 and decreased 18:2w6 and 20:4w6 products relative to an w-6 supplemented group. Urinary PGI3 metabolites are also increased but there was no evidence of a decrease in PGI2 metabolism. Hydroxy-docosahexaenoates (HDHE) have been biosynthesized for pharmacological experiments in which it was observed that they have a weak contractile action on smooth muscle and can also antagonize thromboxane- induced contractility. Platelet HDHEs were steroselectively formed but the brain p0roducts appear to be racemic mixtures.